President Raul Alfonsin on Saturday ordered the army to crush a three-day revolt by rebel troops, and thousands of citizens poured into the streets to rally for democracy.

Alfonsin went on national television after government troops allowed hundreds of mutinous, heavily armed soldiers to leave an infantry school they had seized and move to a new military base. He told the nation that he has ordered the army to "suffocate" the rebellion.The mutinous soldiers began their revolt Thursday to protest the criminal trials of officers who have been charged with committing human rights abuses during the military dictatorships that ruled the country from 1976-83.

Alfonsin, who spoke slightly more than three minutes, described the revolt as a "seditious attempt" against "well-being, tolerance and liberty." He assured citizens that the revolt "does not endanger the republic nor the constitution."

The government broadcast repeated pleas on television Saturday for citizens to rally for democracy. Thousands of people were reportedly gathering in streets and squares throughout the country.

Several ambassadors arrived at the Congress building in Buenos Aires, including Theodore Gildred of the United States. "We are here to lend our complete solidarity to the consolidation of democracy," Gildred said.

The U.S. Embassy issued a statement that said President Reagan and President-elect George Bush sent "their firm and unwavering support" for Argentine democracy.

Alfonsin met with aides and Cabinet members Saturday in the heavily guarded Government House.

Congressman Cesar Jaroslavsky of Alfonsin's governing Civic Radical Union Party called on citizens to "go into the street to defend democracy."

"This is the moment," Jaroslavsky said.

He acknowledged that loyal armed forces members "have not been able to dominate the rebels."

Juan Carlos Pugliese, president of the House of Deputies, said "Democracy is in danger," and called the insurrection "a clear coup attempt."

The insurrection began shortly before dawn on Thursday when about 400 soldiers deserted their posts under the leadership of the charismatic Col. Mohamed Ali Seineldin.

The group, joined later by about 50 coast guard members, seized an infantry school Friday morning at the giant Campo de Mayo military base 22 miles northwest of the capital.

Government forces and tanks surrounded the base and exchanged several rounds of mortar and rifle fire with the rebels Friday, during which four people were wounded, the army said in a communique Saturday. News reports said one person was killed, but there was no official confirmation.

On Saturday, the rebels left the base in army trucks. Government forces did not fire on the rebels, the official news agency Telam said. It said the rebels drove past the government troops aboard several trucks, which they had loaded with weapons and ammunition.

Telam said the rebels arrived a few minutes later at a motorized military unit in Villa Martelli about eight miles away. The unit's officers earlier had been reported as sympathizing with the rebels.

The rebels fortified their positions and set up snipers. At least six tanks were seen.

Presidential spokesman Jose Ignacio Lopez acknowleged Saturday evening that Cabinet ministers and military chiefs meeting at Government House were "nervous," and noted the presidential guard was being reinforced.

Military uprisings in 1987 and earlier this year were led by Lt. Col. Aldo Rico, now discharged and imprisoned. They also were called to support fellow officers being prosecuted in civilian courts for human rights abuses during the dark days of Argentina's military dictatorships.

During the dictatorships, kidnappings, bombings and assassinations by leftist groups were curtailed, but at least 9,000 Argentines "disappeared" and were presumed executed by security forces.